Method for making an axle spindle

ABSTRACT

A spindle for an axle is capable of supporting a vehicle wheel which is rotatably mounted thereon. The method for forming such a spindle includes providing a hollow tubular blank having a generally uniform external diameter and wall thickness and forming the blank to generally reduce its diameter to thereby provide a pair of axially separated wheel bearing mounting regions for supporting the vehicle wheel. A portion of the blank inwardly of the inner bearing region is provided a frusto-conical outer surface. A collar having an inner surface to match the taper of the frusto-conical surface is installed thereon for providing an axial stop for the adjacent bearing. Several alternative methods are provided for securing the collar thereon.

This is a continuation of application Ser. No. 62,714, filed Aug. 1,1979, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for making a spindle for an axle and,more particularly, to a method of forming a tubular blank having auniform cross section and thickness to provide the general contour ofthe spindle and then securing a collar thereon to act as a bearing stop.

2. Description of the Prior Art

There remains a continuing need for reliable, safe and lightweight axlesand/or axle spindles for heavy duty trucks and trailers. An axle of thisgeneral type is disclosed in U.S. Pat. No. 3,037,818 to include at eachspindle an outer first bearing and an inner second bearing forsupporting the wheels. One area of concern when providing axles and axlespindles for these heavy duty vehicles is that adequate support andstrength will be provided in the area of the wheel bearings.Consequently, for the inner wheel bearing, the spindle has generallybeen provided an integral, radially extending bearing stop and thespindle is generally thickened in this region to provide the desiredstrength. The bearing stop establishes the location of the wheelrelative to the end of the spindle with a retaining nut being used tosecure the wheel on the spindle as the inner bearing is forced againstthe bearing stop. While U.S. Pat. No. 3,037,818 discloses one method forforming such an axle and spindle, U.S. Pat. Nos. 3,465,418; 3,501,202;3,535,002 and 3,564,896 present different methods for forming the axlebut again include the two bearing mounting areas and a rigid, integrallyformed bearing stop for the inner bearing.

While there has heretofore been disclosed a number of methods of formingan axle or an axle spindle from a generally tubular blank which mighttend to save weight and material, there remains some question regardingthe applicability of these methods for the particular heavy duty use forwhich the present invention is intended. For example, U.S. Pat. Nos.1,091,751; 2,133,091 and 2,133,092 all disclose how a tubular blankhaving a uniform external diameter and a uniform thickness can begenerally formed to provide the bearing mounting regions mentioned abovefor support of a vehicle wheel. However, since no provision isspecifically made in these axle spindle configurations for providing arigid bearing stop for the inner bearing, it is doubtful that such axlespindles could be utilized in the heavy duty environment expected forthe present invention.

U.S. Pat. No. 3,701,564 appears to disclose that a spindle of thedesired type can generally be formed by cold working a tubular blank toinclude a radially extending bearing stop while still maintaining agenerally uniform wall thickness. However, there is some doubt that sucha product could be satisfactorily employed. Generally, it has been foundthat the forces on an integrally formed bearing stop for the innerbearing are so significant that the resulting concentration of stressesat the transition between the bearing mounting region and the bearingstop have required the thickness of the spindle to be significantlyenlarged in this area.

In fact, there have even been some axle spindles which have been formedfrom tubular blanks which initially were provided a non-uniformthickness to insure that additional metal would be retained in thebearing mounting region after the basic reduction in this area wascompleted.

It can be seen that a number of prior art axle spindles areinappropriate for use on heavy duty vehicles since no rigid bearing stopis provided. Other configurations appear to be appropriate for such usebut require additional material and weight to provide adequate strengthfor such a bearing stop when it is integrally formed with the rest ofthe spindle. The use of any other type of a bearing stop on the spindlemay have been considered inadequate for heavy duty use if, in fact, itwas ever even considered as an alternative in the past. Although U.S.Pat. No. 313,517 appears to generally disclose that a separate collarmay be installed as a bearing stop on an axle, this disclosure would notappear to be applicable for the expected heavy duty use. Rather thanrequiring two bearings of the present configuration, the disclosedtubular axle requires one large tapered bearing for wheel support. Eventhough the taper would significantly reduce the forces on the collar, itshould be noted that this prior art configuration nevertheless includesa thickened basic spindle and is even provided additional materialwithin the spindle for added strength in the collar region.

SUMMARY OF THE INVENTION

Therefore, it is an object of this invention to provide a method formaking reliable, safe and lightweight axles and/or spindles for heavyduty trucks and trailers.

It is a further object to provide a method for taking a tubular blank ofuniform cross section, forming it and adding an axle bearing stopsurface to produce a lightweight axle for heavy duty trucks andtrailers.

It is a still further object of this invention to provide a method forcircumferentially cold forming a tubular blank having a uniform innerand outer diameter and to secure a bearing stop collar thereto tosubstantially reduce stress in the axle spindle as well as reducing thecost of manufacture.

To provide for these and other objects of the invention, a preferredmethod of forming a spindle for an axle capable of supporting a vehiclewheel rotatably mounted thereon includes providing a hollow tubularblank having a central axis, a generally uniform external diameter andwall thickness and a first open end. The tubular blank is then reducedat a first region thereof concentric with the central axis adjacent thefirst end to provide a first diameter thereof and a second regionthereof concentric with the central axis remote from the first end toprovide a second diameter which is greater than the first diameter andless than the external diameter. A first transition area formed betweenthe first region and the second region and a second transition areahaving a generally frusto-conical outer surface is formed between thesecond region and a portion of the tubular blank which is free of thereducing the remote from the first end. A collar is provided having aminimum inner diameter greater than the second diameter for limitedclearance therebetween and including a frusto-conical inner surfacewidening from the minimum inner diameter to match the taper of thesecond transition area. The collar has a radial surface at its innerdiameter which is generally perpendicular to the axis of the collar. Thecollar is mounted on and secured to the second transition area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of a prior art spindle end of a tubularaxle with the bearing assemblies shown in phantom.

FIG. 2 is a sectional view of the final machined axle spindle of thepresent invention.

FIG. 3 is a sectional side view of the tubular blank used in the methodfor forming an axle spindle.

FIG. 4 is a sectional side view of the tubular blank after being reducedby the first forming tool.

FIG. 5 is a sectional side view of the tubular blank after being reducedby the second forming tool.

FIG. 6 is a perspective view of the collar prior to its being secured tothe formed portion of the axle spindle.

DESCRIPTION OF THE INVENTION

As seen in FIG. 1, a prior art axle spindle is adapted to rotatablysupport a wheel (not shown) mounted on a wheel hub 12 at a pair ofaxially disposed wheel bearing assemblies 14 and 16. The outer bearingassembly 14 and the inner bearing assembly 16 are respectively receivedat an axially separated pair of cylindrical bearing regions 18 and 20 ofthe spindle 10. During installation, the bearing assemblies 14 and 16are installed within the central opening of the wheel hub 12 and the hub12 is axially positioned on the spindle 10 to locate the inner bearingassembly 16 against an integral, radially extending bearing stop 22 ofthe spindle 10. The inner bearing region 20 has a larger externaldiameter than the outer bearing region 18 to facilitate assembly. An oilseal 24 is provided at the interior side of the wheel hub 12 to makesliding contact with an exterior surface 26 of the spindle 10 to insurelubrication will be retained at the inner bearing assembly 16 duringwheel operation.

A locking nut assembly 28 is installed on the threaded end 30 of thespindle 10 to apply axial force to the wheel hub 12 as the inner bearing16 is forced against the bearing stop 22. A hub cap (not shown) and asuitable means for sealing the central opening 32 of the spindle 10 atend 30 are provided to protect the locking nut assembly 28 and toestablish the wheel lubrication area at the exterior side of the wheelhub 12.

As mentioned hereinabove, there presently exists a number of methods forforming an axle spindle of the type generally shown in FIG. 1. Spindlesfor trailer or drive axles might be integrally formed or welded to acentral beam or axle housing extending to the right of FIG. 1 (notshown). Although the general configuration of spindle 10 is typical of anumber of spindles presently in use, the portion of the axle between thespindles might be shaped or designed differently depending on thefunction of the axle. For example, the beam of a trailer axle might havea circular or rectangular cross section without affecting the dimensionof the spindle needed to support the wheel. Although the exteriorsurface 26 of the spindle at the bearing seal 24 must be cylindrical forproper sealing, the shape required for a proper transitional area tojoin with the center portion of the axle will not alter the spindle 10as described above.

Similarly, spindles found on steering axles do not typically extend tothe right of the oil seal 24 as shown in FIG. 1. Instead, the spindle isshortened to extend from a steering knuckle which is, in turn, pivotallyjoined to a steering axle beam. It is well known in the art thatdifferent wheel hub mounting means, bearing seals and the addition ofvarious types of brake assemblies would, similarly, not alter the basicspindle configuration requiring two axially separated bearing regionshaving different diameters and a bearing stop adjacent the inner bearingregion for proper receipt and retention of the wheel hub on the spindle.

It is a primary concern in all axle configurations of the type describedthat the spindle be provided adequate strength for supporting the wheelthroughout operation of the heavy duty truck and/or trailer. It has beenfound that the spindle is subject to significant stress in the bearingstop region. Hot forging or otherwise forming the spindle 10 to providean integrally formed shoulder 34 to provide the bearing stop 22 requiresan abrupt transition in the outer configuration of the spindle at 36causing a high concentration of stresses in this region. Compounding theproblem is the fact that some forming methods alter the crystalinestructure of the metal as it is being worked to provide this transitionwhich would further decrease its ability to withstand stress whencompared to the strength at other locations along the length of theaxle. Consequently, the spindle 10 is typically provided an additionalconcentration of metal at 38 which increases the strength of the spindlein this region but significantly adds to its overall weight and to theamount of metal required for its formation. There is a continuing needto decrease the overall weight of heavy duty trucks and trailers toreduce fuel requirements and to minimize the raw material expenses whichadd to the overall manufacturing costs.

As seen in FIG. 2, the preferred axle spindle 40 provides an overallexterior configuration similar to the prior art spindle 10 of FIG. 1.The spindle 40 will support a wheel and wheel hub configurationidentical to that depicted in FIG. 1. A first end 42 is threaded andincludes an outer wheel bearing region 44 having a cylindrical outersurface with a diameter D₁ to receive the outer wheel bearing assemblythereon. The inner bearing region 46 has a cylindrical outer surfacewith a diameter D₂ which is larger than the diameter D₁. The innerbearing region 46 is axially separated from the region 40 with agenerally frusto-conical transition region 48 therebetween.

A radially extending bearing stop surface 50 and an oil sealing surface60 are again provided adjacent the inner bearing region 46. However,unlike the prior art devices, the bearing stop surface 50 and oilsealing surface 60 are located on a non-integral collar 52 which iswelded or otherwise secured to spindle 40. The collar 52 includes atapered frusto-conical inner surface 54 to be closely received on afrusto-conical outer surface of a transition region 56 between the innerbearing region 46 and the main spindle portion 58 located remote fromthe end 42.

As seen in FIG. 6, the collar 52, prior to installation on the majorportion of the spindle 40, includes the outer cylindrical surface 60 anda narrow radially extending rear surface 62 remote from the bearing stopsurface 50. The interior surface includes a narrow cylindrical portion64 in addition to the frusto-conical surface 54 to provide a minimuminternal diameter which is slightly larger than the diameter D₂ of theinner bearing region 46.

Returning to FIG. 2, it can be seen that collar 52 is preferably securedto the transition region 56 by arc welding at 66. The spindle 40 isrotated as the weld 66 is provided along the entire circumference of therear surface 62. Welding in this region causes the forces acting on thecollar 52 during axle use to be displaced from the region immediatelyadjacent the inner bearing region 46 to prevent the stressconcentrations that existed in the prior art spindles. As an alternativeto arc welding, friction welding or the use of a metal-to-metal bondingmaterial could also be employed to secure the collar 52. In some axleconfigurations, it is possible that the region 56 and the inner surface54 of the collar 52 could be provided a locking taper so that the collar52 could be axially forced on the region 56 and locked in positionthereon without any need for welding or bonding. In any case, the collar52 is provided the interior cylindrical portion 64 to insure that a gap68 (shown enlarged in FIG. 2) exists between the collar 52 and theregion 56 adjacent the inner bearing region 46. It is desirable for allmethods of securing the collar 52 to prevent rigid bonding or weldingadjacent the inner bearing region 46 which might produce the undesiredhigher concentration of forces which exist at the integrally formedbearing stop of the prior art spindles.

Either before or after the collar 52 is added to the remaining portionof the spindle 40, the spindle 40 is finished by methods well known inthe axle art. For example, the end 42 is threaded and the bearingregions 44, 46 and the bearing stop surface 50 are provided a finalmachining and induction hardening. However, the cross section of thefinished spindle 40 of FIG. 2 can be seen to be quite different fromthose of the prior art designs discussed hereinabove. The use of anon-integral collar allows the remaining portion of the spindle 40 to belighter while retaining the desired strength characteristics. Thegradual reduction in diameter from the center to the end of the spindlewithout extreme transitions or discontinuities eliminates the need foradditional metal within the spindle so that a relatively uniformthickness can be provided. While the tubular configuration might beprovided through a number of forming methods, it is preferable to beginthe formation from a tubular blank of steel or other suitable metal.Consequently, for trailer axles, for example, it would now be possibleto provide a single tubular blank that can be initially shaped in thecenter to form the beam portion with any desired cross section.Additional formation of the ends of the blank would provide the spindleregions. Although hot swagging methods could be employed, the preferredmethod includes cold forming which would reduce the energy required toform the axle and thus further reduce the overall cost of manufacture.

As seen in FIG. 3, a preferred tubular blank 70 is cylindrical in shapewith the outside diameter D₃ and a uniform thickness T. The length L ofthe blank 70 would be less than the length of the finished axle as shownin FIG. 2 and can be predetermined by those skilled in the metal workingart. The length would depend on the particular metal employed, thediameter and wall thickness of the blank and the exact configurationdesired for the spindle region. It is also known that if the abovementioned parameters are identical, the length might still be differentdepending on whether hot swaging or cold forming is to be employed.

In a typical axle produced by the preferred method of cold forming, thetubular blank would have an outer diameter of 5 inches, a wall thicknessof 0.5 inch and a length of approximately 76 inches. The finished axleincluding spindles 40 would have an overall length of about 81 incheswith the outer bearing region and inner bearing region, respectively,having outer diameters of about 2.6 and 3.5 inches. The collar 52 wouldhave a height of about 0.6 inch and an axial length of about 1 inch.

As seen in FIG. 4, the first step of cold forming basically reduces theblank 70 to provide the transition region 48 and to increase thediameter of the remaining end 72 of the spindle region to the diameterD₂. Cold forming is preferably accomplished by the use of a plurality ofradially, inwardly moving dies 74 (only two of which are shown). In onesuch cold forming machine, twelve dies are circumferentially disposedabout the blank 70 with only an 0.8 inch gap therebetween when the dies74 are all inwardly positioned to form the blank 70. Although the coldforming machine can basically provide the spindle with the shape shownin FIG. 4 with only one inward and outward cycle of the dies 74, it isnot uncommon in this type of recucing operation to rotate the workproduct for a second cycle to provide uniform reduction of the metalincluding the metal remaining between the gaps during the first cycle.It will be noted that after the first step is completed, the spindleregion is elongated from the original length L and the tubular thicknesshas slightly increased from the original thickness T.

As seen in FIG. 5, the second step of cold forming is similar to thefirsrt step. A different set of twelve dies 76 further reduces theremaining end 72 to complete the definition of the inner bearing region46 and to provide the transition region 48 and the end 42 of the spindle40.

In circumferential cold forming of the type described, some practicallimitations exist regarding the amount of reduction that can beaccomplished in a single step. The gaps between the dies at the inwardposition can result in too great a space between the dies when they areall fully retracted if the required radial deformation is too great.Consequently, two steps are desired for the preferred spindle 40 but itis possible that some spindle configurations might allow a single coldforming step and that a non-integral collar could eliminate the extremetransition requirements and thus insure better strength and weightcharacteristics for the spindle.

Although the preferred axle spindle and method of forming the same hasbeen described hereinabove, it can be seen that one skilled in the artcould provide a different spindle or alter the method of formationwithout departing from the invention as claimed.

I claim:
 1. A method of forming a spindle for an axle capable ofsupporting a vehicle wheel rotatably mounted thereon, said methodcomprising: providing a hollow tubular blank having a central axis, agenerally uniform external diameter and wall thickness and a first openend; reducing said tubular blank at a first region thereof concentricwith said central axis adjacent said first end to provide a firstdiameter therefor and a second region thereof concentric with saidcentral axis remote from said first end to provide a second diameterwhich is greater than said first diameter and less than said externaldiameter; forming a first transition area between said first region andsaid second region and a second transition area having a generallyfrusto-conical outer surface between said second region and a portion ofsaid tubular blank which is free of said reducing and remote from saidfirst end; providing a collar having a minimum inner diameter greaterthan said second diameter for limited clearance therebetween andincluding a frusto-conical inner surface widening from said minimuminner diameter to match the taper of said second transition area, saidcollar having a radial surface at said minimum inner diameter which isgenerally perpendicular to an axis of said collar; mounting said collaron said second transition area; and securing said collar to said secondtransition area.
 2. The method as set forth in claim 1, wherein the stepof securing said collar is accomplished by electric arc welding.
 3. Themethod as set forth in claim 2 wherrein said arc welding is confined toa location on said collar remote from said minimum inner diameter andremote from a portion of said second transition area adjacent saidsecond region.
 4. The method as set forth in claim 1, wherein the stepof securing said collar is accomplished by friction welding.
 5. Themethod as set forth in claim 1, wherein the step of securing said collaris accomplished by metal to metal bonding material being applied betweensaid collar and said second transition area with axial force beingapplied to said collar until said material becomes fixed.
 6. The methodas set forth in claim 1, wherein said steps of reducing at said firstand said second regions and forming said first and second transitionareas are accomplished by circumferentially cold working said tubularblank.
 7. The method as set forth in claim 6, wherein a first step ofcold forming includes forming said second region and said secondtransition area and reducing the said blank at said first region andsaid first transition area to provide an interim diameter therefor whichis equal to said second diameter and a second step of cold forming tocomplete the formation of said first region and said first transitionarea.
 8. The method set forth in claim 1, further including machiningsaid first region and said second region for receipt of bearingassemblies thereon for mounting said wheel on said spindle.
 9. Themethod as set forth in claim 1, further including machining said radialsurface of said collar for receipt of a bearing assembly for said secondregion against said collar.
 10. A method of forming a spindle for anaxle capable of supporting a vehicle wheel rotatably mounted thereon,said method comprising: providing a hollow tubular blank having acentral axis, a generally uniform external diameter and wall thicknessand a first open end; reducing said tubular blank at a first regionthereof concentric with said central axis adjacent said first end toprovide a first diameter therefor and a second region thereof concentricwith said central axis remote from said first end to provide a seconddiameter therefor; said first diameter and said second diameter beingless than said external diameter; forming a transition area having agenerally frusto-conical outer surface between said second region and aportion of said tubular blank which is free of said reducing and remotefrom said first end; providing a collar having a minimum inner diametergreater than said second diameter for limited clearance therebetween andincluding a frusto-conical inner surface widening from said minimuminner diameter to match the taper of said transition area, said collarhaving a radial distance at said minimum inner diameter which isgenerally perpendicular to an axis of said collar; mounting said collaron said transition area; and securing said collar to said transitionarea.
 11. The method as set forth in claim 10, wherein the step ofsecuring said collar is accomplished by electric arc welding.
 12. Themethod as set forth in claim 11, wherein said arc welding is confined toa location on said collar remote from said minimum inner diameter andremote from a portion of said transition area adjacent said secondregion.
 13. The method as set forth in claim 10, wherein the step ofsecuring said collar is accomplished by friction welding.
 14. The methodas set forth in claim 10, wherein the step of securing said collar isaccomplished by metal to metal bonding material being applied betweensaid collar and said second transition area with axial force beingapplied to said collar until said material becomes fixed.
 15. The methodas set forth in claim 10, wherein said steps of reducing at said firstand said second regions and forming said transition area areaccomplished by circumferentially cold working said tubular blank. 16.The method as set forth in claim 10, further including machining saidfirst region and said second region for receipt of bearing assembliesthereon for mounting said wheel on said spindle.
 17. The method as setforth in claim 10, further including machining said radial surface ofsaid collar for receipt of a bearing assembly for said second regionagainst said collar.